Study On Reaction Mechanism Of Phenol Degradation By Activation Of Persulfate With Zirconium Based Nanomaterials

Recently,extensive attention has been paid to advanced oxidation technology based on persulfate,which has the advantages of strong oxidation,safe and convenient storage and transportation,and action without secondary pollution.Many methods have been used in persulfate activation.Heterogeneous catalyst activation has been widely concerned for its high efficiency and easy recovery.Transition metals and their oxides are mainly studied in heterogeneous catalyst.The traditional transition metal-based catalysts have metal leaching problems,which lead to the degradation of catalyst performance and secondary pollution.Therefore,it is urgent to develop an efficient and stable catalyst for persulfate activation.An ideal substrate with good physical and chemical stability,large surface area and wide band gap but less structural defects and poor conductivity could be found in pure Zr-containing material.Pyrolytic carbon doped materials have rich function groups and defect structures,which can make up pure Zr-based materials.Further more,the edge nitrogen brought by carbon-nitrogen doping played a great role in promoting the PS'activation.Hybrid mode based on“solid-liquid(S-L)”and“liquid-liquid(L-L)”were employed,and solid and soluble Zr-based precursors were selected.Phenol was used as the target compound for its simplest phenolic structure.The main research contents and conclusions are as follows:(1)Nitrogen doped zirconium carbide composite with zirconium based catalyst(N-Zr C)were prepared through“S-L”mixing methods.The catalyst was characterized by Scanning electron microscope(SEM)and mapping,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared(FTIR)spectroscopy.N-Zr C nanoparticles are 50-200 nm in diameter and uniformly N-doped structure.Zr C,Zr O₂ and Zr N were present in 12 at%of the nano particle.Carbon-nitrogen doping forms rich functional groups such as pyrrole N and pyridine.The catalyst was used to active both PMS(0.103 min^-1)and PDS(0.0930 min^-1),and phenol was removed within 40 min.(2)A nano nitride-doped carbon-zirconia(N-C/Zr O₂)was fabricated via a facile thermal pyrolysis method using“S-L”mixing methods.The N-C/Zr O₂ was used to catalyze persulfate activation for phenol degradation and its physicochemical properties were exanimated by SEM,XRD,XPS and FTIR.The result showed that the as-fabricated N-C/Zr O₂ catalyst with4.9%N-doping and a particle size of<50 nm revealed an excellent catalytic capability(0.124min^-1)in phenol removal and reached 58.3%mineralization.It also showed little effect on phenol degradation with coexistence of Cl^-,Ca²⁺,Mg²⁺and humic acid in water.(3)The morphology and structure of doped materials with“S-L”mixing methods were a C-N around the“Solid”material,while more uniform and finer doped was prepared with“L-L”mixing methods.Urea's doping endows the material with active functional groups and fluffy nano-structure,which greatly improves the catalytic performance of the material.The reaction process fitted with the pseudo first-order reaction kinetics in both N-Zr C/PS and N-C/Zr O₂/PS system.“L-L”mixing methods showed better activation of the catalyst,while the dosages of catalyst and PS were only half of“S-L”.It suggested that ¹O₂ and O₂^·-were primary reactive oxygen species(ROS)through the scavenger experiment and Electron paramagnetic resonance(EPR).This study demonstrated that the N-C-doped Zr-based nanomaterials in activating persulfate can be considered as a promising technology for the removal of aqueous organic contaminant.